The off-duty agent hit the car, but the gunman drove away, police said. Authorities later arrested John T. Earnest, 19, along Interstate 15. A rifle was found in the front passenger seat, police said.

"Mr. Stewart risked his life to stop the shooter and saved lives in the process," the sheriff's department said in a statement.

Oscar Stewart of Rancho Bernardo, was the one who screamed at the suspect, 19-year-old John Earnest, and ran him out, gives media interview from the horrific incident at the memorial site across Chabad of Poway synagogue.(Photo: Nick Oza, The Arizona Republic)

Stewart's heroics didn't stop there. The man said he rushed back into the synagogue where he saw Rabbi Yisroel Goldstein bleeding from his hand and congregant Lori Gilbert-Kaye on the ground.

"I immediately went to the lady on the floor and started doing CPR on her. She didn’t make it," Stewart said.

According to the San Diego Union-Tribune, Stewart said he served in Iraq from March 2003 to April 2004. He had also been a bomb disposal tech in the Navy, and joined the Army after the September 11 terrorist attacks.

"I never thought I’d hear gunfire again," he told the Union-Tribune.

Goldstein said Morales recently discovered his Jewish roots and traveled more than three hours from El Centro to pray with the congregation. The rabbi recalled telling Morales, “Please arm yourself when you are here. We never know when we’ll need it.”

San Diego County Sheriff Bill Gore, center, speaks at a news conference held outside of the Chabad of Poway Synagogue Saturday, April 27, 2019, in Poway, Calif. One person was killed and three injured in a shooting at the synagogue. Denis Poroy, AP